When applying induction heating to a workpiece having a rotation axis, the workpiece is heated by induction heating while being rotated around the rotation axis so as to uniformly heat the workpiece. Induction heating equipments are generally small in size and are capable of high-speed heating with excellent repeatability, and therefore are suitable for incorporation in a manufacturing line and automation.
A related art heat treatment apparatus is configured to apply quenching on an outer peripheral surface of a workpiece, a cam portion of a cam shaft, while rotating the cam shaft (see, .e.g., JP2012-31464A), and induction heating and cooling of the workpiece are automated. In quenching, cooling of the workpiece affects the quenching quality. Accordingly, in the related art heat treatment apparatus, cooling liquid sprayed to the workpiece is collected, and based on presence or absence of a flow of the collected cooling liquid or the flow rate of the collected cooling liquid, whether the cooling liquid has been properly sprayed is detected.
FIG. 4 shows a configuration of an example of a heat treatment apparatus for performing induction heating on a hub ring as a workpiece having a rotation axis.
A heat treatment apparatus 101 shown in FIG. 4 includes a pair of support portions 103a, 103b and a heating coil 105. The support portions 103a, 103b support opposite axial end portions of a hub ring 102 and can be driven to rotate. A shaft portion 104 of the hub ring 102 is inserted into the heating coil 105. Induction heating is performed on the outer peripheral surface of the shaft portion 104 while rotating the hub ring 102.
The support portion 103b supporting an end portion of the hub ring 102 on the side of a flange 106 includes a rotary shaft 108 and a fixing base 110. A discharge nozzle 107 for spraying cooling liquid to the end portion on the flange 106 side is provided in the rotary shaft 108, which supports the hub ring 102. The fixing base 110 is coupled to the rotary shaft 108 via a rotary joint 109. A cooling liquid supply source is connected to the fixing base 110.
During the heating of the shaft portion 104, the cooling liquid is supplied inside the fixing base 110 and the rotary joint 109 and then inside the rotary shaft 108. The supplied cooling liquid is sprayed from the discharge nozzle 107 toward the end portion of the hub ring 102 on a side of the flange 106. Thus, it is suppressed that parts on which heat treatment is not required (for example, the end portion on the flange 106 side, the flange 106, etc.) may be also heated and increased in temperature to change their physical properties.
Here, when there arises such a trouble that the rotary joint 109 as a movable portion falls off, the cooling liquid cannot be supplied to the rotary shaft 108 on the downstream of the rotary joint 109 along a supply passage of the cooling liquid. Thus, there may arises an event that the cooling liquid cannot be properly sprayed.
Also with the heat treatment apparatus 101 having the configuration described above, the sprayed cooling liquid can be collected and whether the cooling liquid has been properly sprayed can be detected based on presence or absence of a flow of the collected cooling liquid or the flow rate of the collected cooling liquid However, in order to collect the cooling liquid in a reliable manner, the discharge nozzle 107 and the hub ring 102 may need to be surrounded with a housing to suppress scattering of the cooling liquid, and this may cause a trouble in carrying the hub ring 102 in or out.
If a detection is made as to the presence or the absence of a flow of the cooling liquid or the flow rate cooling liquid inside the rotary shaft 108 at a location downstream of the rotary joint 109, the housing for collecting the sprayed cooling liquid can be omitted. However, it is difficult to provide a detector to the rotary shaft 108 to be rotated.